Statistical Methods in HIV/AIDS Research Project Summary The objective of this methods proposal is to develop and apply new statistical methods to improve scientific inferences for data collected in HIV/AIDS research, specifically aiming to: (1) develop a general class of regression models to study residual time in HIV treatment and prevention efficacy trials. The developed methods will be applied to determine in residual time whether early versus delayed ART initiation is important in patient's time to AIDS-defining illness or death, and to further explore the clinical factors which are important in governing the progression to AIDS or death after ART initiation;(2) develop statistical methods for recurrent event and marker process data that exhibit a terminal behavior before an informative failure event. The developed methods will be applied to examine the correlation between treatment regimens and the complete history of recurrent events such as opportunistic infections, taking into account variables available to clinicians in the course of routine care;(3) develop statistical methodologies to infer causal treatment effect from complex longitudinal data in randomized HIV prevention trials. PUBLIC HEALTH RELEVANCE: Statistical Methods in HIV/AIDS Research Project Narrative This proposal aims to develop statistical methods in HIV/AIDS research. Specifically, these methods are targeted to regression analysis of censored residual life, analysis of recurrent markers in the presence of terminal events, and informative censoring and causal inferences of treatment efficacy in complex HIV/AIDS clinical trials. Upon successful completion of the project, the proposed methods shall provide a collection of new statistical tools for resource planning, clinical consulting and efficacy assessment in HIV/AIDS research.